A conventional cutting process is performed by biasing a cutting tool including a cutting tool insert against a workpiece (target object) that is being rotated. However, in such a cutting method, a cutting point in the cutting tool insert during the cutting process is unchanged, with the result that resultant cutting heat and cutting load are concentrated on the cutting point.
In order to solve the problem of such a conventional cutting process, a spinning process has been introduced (for example, Patent Document 1). In the spinning process, a rotary cutting tool including a rotary cutting tool insert and rotating around an axis is biased against a workpiece that is being rotated, thereby cutting it with a cutting edge continuous in a direction of rotation of the tool. In such a spinning process, the cutting point of the rotary cutting tool insert is changed moment by moment during the cutting process. Therefore, the rotary cutting tool insert, which has been heated by generated cutting heat, is cooled during the rotation of the rotary cutting tool. Moreover, during the rotation, cutting load on the rotary cutting tool insert is distributed over the entire circumference of the cutting tool insert.
As a result of cutting the workpiece by the cutting tool insert, swarf is inevitably generated. When long, continuous swarf is generated, the swarf is wound around the workpiece, thus damaging a finished surface of the workpiece, disadvantageously. In view of this, in order to avoid such long, continuous swarf, the swarf needs to be handled appropriately.
However, the cutting tool insert described in Patent Document 1 is not provided with a breaker for cutting generated swarf to be short, with the result that the generated swarf cannot be handled appropriately, disadvantageously.
In order to cope with such a problem, there has been proposed a rotary cutting tool insert in which a projection is provided at an upper portion of a cutting edge thereof. Also, there has been proposed a rotary cutting tool insert in which a groove is provided at a portion of a cutting edge thereof (for example, Patent Document 2 and
Patent Document 3).